Page 178 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 147

of foals (it is rare in adult horses due to the • ‘Lungworm’ – Dictyocaulus sp., the adult
development of immunity) and causes diarrhoea worms live in the trachea and bronchi of the
and ill-thrift. Ascaridia galli occurs in poultry host and cause bronchitis with coughing and
and other birds. Other species which may be of loss of weight. The clinical signs may vary
clinical significance in birds include Heterakis sp., depending on the presence of concurrent
Porrocaecum sp. and others. disease(s). In host adapted infections, where
the animal has some immunity, the disease
may be mild but in some cases the animal
Disease process and clinical signs
may develop an allergic response to migrating
Larval and adult ascarids may cause significant larvae and develop severe acute pneumonia.
damage to the lungs, liver and intestine. The Dictyocaulus viviparus is the species seen in
clinical signs may include weakness and stunted cattle and deer, D. filaria occurs in sheep
growth in young animals. Heavy infections and goats and D. arnfieldi occurs in horses
result in a potbellied appearance, poor coat and and donkeys. Donkeys may have sub-clinical
diarrhoea, which alternates with constipation. In lungworm infections resulting in contami-
dogs, vomiting may also occur. nation of pasture which may lead to clinical
disease in horses grazing in the same local-
ity. Generally, in areas where lungworm is a
Diagnosis
problem, horses and donkeys should not be
1 Clinical signs. grazed together. Diagnosis is made by exam-
2 Faecal examination for parasite eggs. ining the faeces for the presence of lungworm
larvae which hatch from the egg during pas-
sage through the gastrointestinal tract after
Treatment
being coughed up and swallowed by the host
There are a wide range of anthelmintic drugs (see Figure 3.25). A modified Baermann tech-
that can be used and guidance should be sought nique can be done to identify the larvae (L1)
from the local animal health advisor or veteri- in the faeces. Blood samples may also be col-
nary surgeon. Hygiene and good husbandry are lected for serological examination (CFT and
important in order to prevent re-infection of ELISA, see Chapter 6). The disease is treated
treated young animals. by removing infected animals to clean graz-
ing after treatment with anthelmintics. There
are also vaccines available for cattle which are
nematodes that live in the lungs derived from irradiated larvae.
• Ovine lungworm – Muellerius sp., the adults
The clinical disease associated with lungworm live in the large bronchi and bronchiolar tissue
infection in animals must be distinguished from resulting in respiratory signs. The parasite has
other causes of pneumonia, such as viral (for an indirect life cycle with molluscs (for example,
example, Parainfluenza, infectious bovine rhinotra- snails) acting as the intermediate host. A modi-
cheitis) and bacterial (for example, Pasteurella sp.), fied Baermann is preferred for detecting L1.
diseases. In many cases a combination of infec- • Porcine lungworm – Metastrongylus sp., the
tious agents may be involved and the first step in adults live in the bronchi resulting in respira-
treatment should be to identify the pre-disposing tory signs. This lungworm has an earthworm
factors and improve husbandry (housing, nutrition, intermediate host. The eggs rather than the
appropriate stocking rates and so on). larvae can be detected in faecal float.

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